In this project we aim to investigate total Hg and methyl Hg in seawater, suspended matter, sediment cores as well as phyto- and zooplankton. Samples were collected in a highly productive area in the South Atlantic around South Georgia during the “ISLAND IMPACT” Polarstern research cruise (Oct./Nov. 2022) at several Deep- and Process Stations. Seawater was sampled down to a max. depth of 7000 m while suspended matter and plankton was sampled to max. 350 and 600 m respectively using nets and large volume in-situ pumps. Sediment cores were taken directly below the sampled water column at a maximum depth of 8000 m (Sandwich Trench). The data of Hg and methyl Hg concentrations will be interpreted in context with basic and extended hydrochemical- and physical parameters such as chlorophyll a, nutrients, redox indicators, particle transformation and fluxes as well as analyses of the chemical composition and the biological origin (phytoplankton, macro or mesozooplankton, fecal pellets etc.) of suspended matter and sediments which will be provided by other participants of the ISLAND IMPACT project.
With this comprehensive data set we aim resolve the biogeochemical cycling of Hg and methyl Hg and to quantify the Hg export in highly productive areas. We hypothesize that phytoplankton blooms cause depletion of Hg in the water column and are hot spots for methyl-Hg formation and Hg export to the sediment. Moreover, we want to prove if decomposition of organic seston on its way through the water column causes depletion of methyl Hg and enrichment of total Hg in sinking particles. We will further decipher if MeHg and THg in zooplankton of areas of intense phytoplankton blooms becomes higher enriched compared to zooplankton of oligotrophic zones.
Projektbeteiligte: Prof. Dr. Harald Biester
Recent findings suggest that tropical ecosystems, particularly tropical forests, are a major component in the global mercury (Hg) cycle. Because of the high productivity and litter production in tropical forests, 70% of the global atmospheric (dry) deposition of Hg to forest topsoils occur in these environments. There has been an increasing interest of the significance of determining the relationship between Hg accumulation in leaves and leaf/canopy characteristics, such as specific leaf area (SLA) and leaf area index (LAI), respectively, to update global Hg models.
This DFG funded project aims to provide a more detailed characterization of the vegetation Hg cycle in tropical forests, including two different forest types Tropical Dry Broadleaf Forest (TDBF) and Tropical Moist Broadleaf Forest (TMBF). The proposed study aims to determine how different tropical forest types and associated climatic conditions drive Hg accumulation in vegetation, as well as its transport from the atmosphere to the soil. Finally, we will quantify Hg accumulation in the organic topsoil and its relationship to carbon accumulation and Hg fluxes in litterfall providing which will provide valuable additional data for future global Hg models.
Projektbeteiligte: Dr. Marta Pérez Rodríguez, Prof. Dr. Harald Biester
The key objective of this project is to quantify the impact of tree water use of distinct deep soil water for tree health and forest stability for key forest species in Europe. To achieve this, we will characterize the spatiotemporal behavior of the different water pools in the unsaturated zone in dependence to precipitation input and groundwater table depth, the spatiotemporal connectivity between trees and these pools and phenological and physiological drought responses of trees along topographic gradients in the field.
Our central hypothesis is that particularly connectivity to the capillary zone is a critical component of drought tolerance. However, its impact for tree health will vary among species (water use strategies, degree of isohydricity) and across sites (climatic conditions and geomorphological gradients).
Projektbeteiligte: Dr. Matthias Beyer, Dr. Maren Dubbert (Leibniz Institute for Agricultural Landscape Research, ZALF, Müncheberg)
Das Projekt QUISS (gefördert von der Bundesanstalt für Gewässerkunde; Teil des größeren Forschungsprojektes Quiss) beschäftigt sich mit der Untersuchung der Fraktionierung, Speziierung, Umwandlungsprozesse und Mobilität von Quecksilber in Sedimenten und Schwebstoffen deutscher Fließgewässer.
Einer der Hauptgründe für die flächendeckend negative Einstufung des chemischen Zustands deutscher Fließgewässer als „nicht gut" ist die Überschreitung der EU-Umweltqualitätsnorm für Quecksilber (Hg) in Biota. Der biogeochemische Hg-Kreislauf in Fließgewässern ist jedoch nur unzureichend verstanden (z.B. Quellen, Senken, Remobilisierung, Einfluss von Mikroorganismen). Ziel des Projektes ist es, handlungsfähiger bei der Bearbeitung aktuell dringlicher Fragestellungen zu Quecksilber in Bundeswasserstraßen zu werden. Auf internationalem Niveau vorhandene Wissenslücken zur Hg-Speziierung in Sedimenten und Schwebstoffen sollen geschlossen werden. Die Ergebnisse sollen dazu beitragen mögliche Einflüsse von Unterhaltungsmaßnahmen auf den biogeochemischen Hg-Kreislauf besser zu verstehen, und letztlich die Entwicklung verbesserter Managementvorschläge und Handlungsanweisungen vorantreiben.
The general objective of this project is to establish a functional, quantitative method for assessing Hg0 concentrations in the gas phase and, by proxy, Hg0 outgassing from aquifers, soils, and peatlands using MerPAS (Hg0 passive air sampler, developed by David McLagan and researchers at the University of Toronto) deployed in groundwater wells and in buried sampling containers in soils and peat, respectively.
While the majority of human and environmental health issues from Hg are related to the highly toxic methyl-Hg (MeHg), the oxidation state, specific compound distribution, and reaction mechanisms in different environmental media as well as the long-range transport potential of these different compounds of Hg are fundamental in controlling the production and distribution of MeHg in the environment.
The primary purpose of EMOSGROW is to develop and implement a quantitative method to monitor gaseous Hg0 concentrations in subterranean compartments via subsurface deployments of the versatile MerPAS and use these data generate estimates of Hg0 outgassing and Hg2+ reduction potential across three spatial dimensions. These data will be complimented by above ground MerPAS measurements of Hg0 concentrations and combined will improve the determination of Hg0 fluxes from and within soil-groundwater systems. Understanding these fluxes has relevance from a human and environmental health perspective due to the potential for the emitted Hg0 to undergo long-range transport, deposition, methylation to highly toxic MeHg, and be taken up aquatic food webs.
Projektbeteiligte: Dr. David McLagan, Prof. Dr. Harald Biester, Dr. Caiyan Feng
As part of the cooperation between the working group "Environmental Geochemistry" of the TU Braunschweig and the Institute of Geography at the University of Costa Rica (UCR) in San José, geochemical investigations on the behaviour of trace elements are carried out in the biological reserve Antonio Manuel Brenes (ReBAMB). The area lies in a tropical pre-montane rainforest and is characterized by steep slopes, tropical climate and its volcanic origin.
